Accurate assessment of the brake torque on a rope-braked cycle ergometer

Sports Engineering - A Monark cycle ergometer is a device globally used in physiological studies to measure the work and energy levels of exercising humans. In this paper a rope-braked cycle...     

3种自行车功率计无氧功率测试结果的比较

采用 Monark 834,Monark 839E,SRM3种自行车功率计对8名优秀男子自行车运动员进行30s Wingate 元氧功率测试(WAT),对测试结果进行比较,分析3种功率计测定参数的异同与自行车实际运动方式的差异。结果表明:Monark834进行 Wingate 测试和自行车运动实践不尽相符。Monark 839E 可以比较精确的反映受试者的起动能力。Monark 834和 Monark839E 进行 WAT 测试时,其预定负荷受到一定的限制。SRM 测试指标的内容和精度较Monark834、Monark 839E要高。从模拟自行车运动实际状况来看,SRM 是更适合自行车运动员测试的专业工具。     

Mechanically braked Wingate powers: agreement between SRM, corrected and conventional methods of measurement

In this study, we assessed the agreement between the powers recorded during a 30 s upper-body Wingate test using three different methods. Fifty-six men completed a single test on a Monark 814E mechanically braked ergometer fitted with a Schoberer Rad Messtechnik (SRM) powermeter. A commercial software package (Wingate test kit version 2.21, Cranlea, UK) was used to calculate conventional and corrected (with accelerative forces) values of power based on a resistive load (5% body mass) and flywheel velocity. The SRM calculated powers based on torque (measured at the crank arm) and crank rate. Values for peak 1 and 5 s power and mean 30 s power were measured. No significant differences (P >0.05) were found between the three methods for 30 s power values. However, the corrected values for peak 1 and 5 s power were 36 and 23% higher (P <0.05) respectively than those for the conventional method, and 27 and 16% higher (P <0.05) respectively than those for the SRM method. The conventional and SRM values for peak 1 and 5 s power were similar (P >0.05). Power values recorded using each method were influenced by sample time (P <0.05). Our results suggest that these three measures of power are similar when sampled over 30 s, but discrepancies occur when the sample time is reduced to either 1 or 5 s.     

Mechanically braked Wingate powers: agreement between SRM,corrected and conventional methods of measurement

In this study, we assessed the agreement between the powers recorded during a 30?s upper-body Wingate test using three different methods. Fifty-six men completed a single test on a Monark 814E mechanically braked ergometer fitted with a Schoberer Rad Messtechnik (SRM) powermeter. A commercial software package (Wingate test kit version 2.21, Cranlea, UK) was used to calculate conventional and corrected (with accelerative forces) values of power based on a resistive load (5% body mass) and flywheel velocity. The SRM calculated powers based on torque (measured at the crank arm) and crank rate. Values for peak 1 and 5?s power and mean 30?s power were measured. No significant differences (P?>0.05) were found between the three methods for 30?s power values. However, the corrected values for peak 1 and 5?s power were 36 and 23% higher (P?<0.05) respectively than those for the conventional method, and 27 and 16% higher (P?<0.05) respectively than those for the SRM method. The conventional and SRM values for peak 1 and 5?s power were similar (P?>0.05). Power values recorded using each method were influenced by sample time (P?<0.05). Our results suggest that these three measures of power are similar when sampled over 30?s, but discrepancies occur when the sample time is reduced to either 1 or 5?s.     

A static method for obtaining a calibration factor for SRM bicycle power cranks

Many scientists and coaches are interested in mechanical power produced during cycling, and use Schoberer Rad Me\technik (SRM) bicycle power cranks to obtain this data. However, it has been expensive and difficult to calibrate SRM cranks, causing much of the collected data to be unreliable. We present a static method, derived from first principles, for obtaining a calibration factor for SRM cranks. A known mass and lever arm (chainring of a known diameter) are used to apply a known torque load to the instrument in four positions, and the output frequencies are used to calculate the calibration factor in Hz/Nm. The reproducibility of this method is ±0.01 Hz/Nm, which is acceptable for the application of the instrument, which is measurement of mechanical power application by cyclists at the crank. The method is reliable, inexpensive, and easy to set up, and will allow higher confidence in data collected using SRM power cranks. We recommend calibration of the power meter once every six months because of the measured drift of the calibration factor over time.     

Reliability and validity of a new double poling ergometer for cross-country skiers

Thirty-eight competitive cross-country skiers were divided into three groups to assess the reliability and validity of a new double poling ergometer. Group A (n = 22) performed two maximal 60-s tests, Group B (n = 8) repeated peak oxygen uptake tests on the double poling ergometer, and Group C (n = 8) performed a maximal 6-min test on the double poling ergometer and a double poling time-trial on snow. The correlation between the power calculated at the flywheel and the power applied at the base of the poles was r = 0.99 (P < 0.05). The power at the poles was 50-70% higher than that at the flywheel. There was a high test-retest reliability in the two 60-s power output tests (coefficient of variation = 3.0%) and no significant difference in peak oxygen uptake in the two 6-min all-out tests (coefficient of variation = 2.4%). There was a strong correlation between the absolute (W) and relative power (W x kg(-1)) output in the 6-min double poling ergometer test and the double poling performance on snow (r = 0.86 and 0.89 respectively; both P < 0.05). In conclusion, our results show that the double poling ergometer has both high reliability and validity. However, the power calculated at the flywheel underestimated the total power produced and needs to be corrected for in ergonomic estimations.     

Agreement between polar and SRM mobile ergometer systems during laboratory-based high-intensity, intermittent cycling activity

The purpose of this study was to assess the agreement between two mobile cycle ergometer systems for recording high-intensity, intermittent power output. Twelve trained male cyclists (age 31.4 +/- 9.8 years) performed a single 3 min intermittent cycle test consisting of 12 all-out efforts, separated by periods of passive recovery ranging from 5 to 15 s. Power output was recorded using a Polar S710 heart rate monitor and power sensor kit and an SRM Powercrank system for each test. The SRM used torque and angular velocity to calculate power, while the S710 used chain speed and vibration to calculate power. Significant differences (P < 0.05) in power were found at 8 of the 12 efforts. A significant difference (P = 0.001) was also found when power was averaged over all 12 intervals. Mean power was 556 +/- 102 W and 446 +/- 61 W for the SRM and S710 respectively. The S710 underestimated power by an average of 23% with random errors of */[division sign] 24% when compared with the SRM. Random errors ranged from 36% to 141% with a median of 51%. The results indicate there was little agreement between the two systems and that the Polar S710 did not provide a valid measure of power during intermittent cycling activity when compared with the SRM. Power recorded by the S710 system was influenced greatly by chain vibration and sampling rates.     

The effect of pedal crank arm length on joint angle and power production in upright cycle ergometry

The aim of this study was to determine the effect of five pedal crank arm lengths (110, 145, 180, 230 and 265 mm) on hip, knee and ankle angles and on the peak, mean and minimum power production of 11 males (26.6+/-3.8 years, 179+/-8 cm, 79.6+/-9.5 kg) during upright cycle ergometry. Computerized 30 s Wingate power tests were performed on a free weight Monark cycle ergometer against a resistance of 8.5% body weight. Joint angles were determined, with an Ariel Performance Analysis System, from videotape recorded at 100 Hz. Repeated-measures analysis of variance and contrast comparisons revealed that, with increasing crank arm lengths, there was a significant decrement in the minimum hip and knee angles, a significant increment in the ranges of motion of the joints, and a parabolic curve to describe power production. The largest peak and mean powers occurred with a crank arm length of 180 mm. We conclude that 35 mm changes in pedal crank arm length significantly alter both hip and knee joint angles and thus affect cycling performance.     

The effect of pedal crank arm length on joint angle and power production in upright cycle ergometry

The aim of this study was to determine the effect of five pedal crank arm lengths (110, 145, 180, 230 and 265 mm) on hip, knee and ankle angles and on the peak, mean and minimum power production of 11 males (26.6 +/- 3.8 years, 179 +/- 8 cm, 79.6 +/- 9.5 kg) during upright cycle ergometry. Computerized 30 s Wingate power tests were performed on a free weight Monark cycle ergometer against a resistance of 8.5% body weight. Joint angles were determined, with an Ariel Performance Analysis System, from videotape recorded at 100 Hz. Repeated-measures analysis of variance and contrast comparisons revealed that, with increasing crank arm lengths, there was a significant decrement in the minimum hip and knee angles, a significant increment in the ranges of motion of the joints, and a parabolic curve to describe power production. The largest peak and mean powers occurred with a crank arm length of 180 mm. We conclude that 35 mm changes in pedal crank arm length significantly alter both hip and knee joint angles and thus affect cycling performance.     

Determination of the peak power output during maximal brief pedalling bouts

The purpose of this study was to propose an optimization procedure for determining power output during very brief maximal pedalling exercise. Twenty-six healthy male students (21-28 years) performed anaerobic tests on a Monark bicycle ergometer with maximal effort for less than 10 s at eight different loads ranging from 28.1 to 84.2 Nm in pedalling moment. The maximal pedalling rate was determined from the minimal time required for one rotation of the cycle wheel. Pedalling rate decreased linearly with the load. The relationship between load and pedalling rate was represented by two linear regression equations for each subject; one regression equation was determined from eight pairs of pedalling rates and loads (r less than -0.976) and the other from three pairs (at 28.1, 46.8, 65.5 Nm; r less than -0.969). The two regression coefficients of the respective regression equations were almost identical. Mean +/- S.D. of maximal power output (Pmax) which was determined for each subject based on the two linear regression equations for eight pairs and three pairs of pedalling rates and loads was 930 +/- 187 W (13.4 +/- 1.6 W kgBW-1) and 927 +/- 187 W (13.4 +/- 1.6 W kgBW-1), respectively. There was no statistically significant difference between the values of Pmax which were obtained from each equation. It was concluded that maximal anaerobic power could be simply determined by performing maximal cycling exercise at three different loads.     

不同踏蹬频率下自行车运动员踏蹬力研究

利用SRM功率车以及安装在功率车上的测力系统(Powertec-System)研究不同踏蹬频率下场地自行车运动员一个踏蹬周期内作用于曲柄的切向踏蹬力特征。以8名自行车运动员为研究对象,在SRM功率车上进行10min、90rpm、120w的准备活动后,进行阻力负荷为500watt的骑行,踏蹬频率分别为100、120、130、140rpm,顺序随机选择,骑行稳定后,采集连续5s的踏蹬力数据。结果表明,随着踏蹬频率的提高,作用在左、右两侧曲柄的切向踏蹬力分量的正均值、均值、最大值减小,两侧切向踏蹬力分量之和的均值及峰值也减小(p<0.01);左、右侧正切向踏蹬力分量的起止位置、最值位置、双侧切向踏蹬力分量之和的峰值位置均随着踏蹬频率的增大而提前(p<0.01);在踏蹬周期的下半段,踏蹬频率越高,切向踏蹬力曲线越低,在踏蹬周期的上半段,踏蹬频率越高,切向踏蹬力曲线越高。     

Agreement between Polar and SRM mobile ergometer systems during laboratory-based high-intensity,intermittent cycling activity

Abstract

The purpose of this study was to assess the agreement between two mobile cycle ergometer systems for recording high-intensity, intermittent power output. Twelve trained male cyclists (age 31.4 ± 9.8 years) performed a single 3 min intermittent cycle test consisting of 12 all-out efforts, separated by periods of passive recovery ranging from 5 to 15 s. Power output was recorded using a Polar S710 heart rate monitor and power sensor kit and an SRM Powercrank system for each test. The SRM used torque and angular velocity to calculate power, while the S710 used chain speed and vibration to calculate power. Significant differences (P < 0.05) in power were found at 8 of the 12 efforts. A significant difference (P = 0.001) was also found when power was averaged over all 12 intervals. Mean power was 556 ± 102 W and 446 ± 61 W for the SRM and S710 respectively. The S710 underestimated power by an average of 23% with random errors of ?/÷ 24% when compared with the SRM. Random errors ranged from 36% to 141% with a median of 51%. The results indicate there was little agreement between the two systems and that the Polar S710 did not provide a valid measure of power during intermittent cycling activity when compared with the SRM. Power recorded by the S710 system was influenced greatly by chain vibration and sampling rates.     

Original characteristics of a new cycle ergometer

The aim of this study was to describe and validate a new cycling ergometer with original characteristics that allow the measurement of biomechanical variables with position and crank inertial load used by the cyclist in field condition. The braking pedalling force, that permitted the simulation of the resistance to the cyclist in the field, is performed with a brushless electric motor. The validity and the reproducibility of the power output measurements were compared with the widely accepted SRM powermeter. The results indicate that taking into account a systematic error, the measurements are valid compared with the SRM, and the reproducibility of the power output measurements is similar to the SRM. In conclusion, this ergometer is the only one that allows at the same time for (1) valid and reproducible power output measurements at submaximal intensity, (2) utilisation of the personal bicycle of the cyclist, and (3) simulation of the inertial characteristics of the road cycling.     

The effects of sodium bicarbonate and pyridoxine-alpha-ketoglutarate on short-term maximal exercise capacity.

The purpose of this study was to determine the effects of the simultaneous use of pyridoxine-alpha-ketoglutarate (PAK) and sodium bicarbonate (NaHCO3) on short-term maximal exercise capacity in eight well-trained male cyclists. The study consisted of the determination of maximal power output and the administration of various combinations of placebos, PAK and NaHCO3, followed by a short-term maximal exercise test. To determine maximal power output (power(max)), the subjects performed a continuous, incremental test on a Monark bicycle ergometer to symptom limited maximum (test 1). To determine the effects of NaHCO3 and PAK on short-term maximal exercise performance, the subjects were administered either placebo (PLA), PAK and sodium bicarbonate (P/B), PAK and placebo (PAK), or sodium bicarbonate and placebo (BIC) prior to performing short-term maximal exercise (test 2). Oral tablets of NaHCO3 and PAK were given in doses of 200 mg kg-1 and 50 mg kg-1 respectively. The subjects pedalled at the power output corresponding to 100% of their VO2 max at 70 rev min-1 until voluntary cessation or until they were unable to maintain pedal revolution rate. Venous blood samples were drawn at rest (RES), cessation of exercise (CES) and after 2 min of recovery (REC) and analysed for lactate, pH and bicarbonate ion concentration. The subjects attained an average maximum power output of 377 +/- 20 W during the graded maximal pre-test (test 1). There were no significant differences between treatments in the ability to sustain power(max) during test 2. During test 2, the subjects were able to sustain power(max) for 7.6 +/- 4.3 min with P/B, 6.7 +/- 2.9 min with PAK, 7.3 +/- 4.9 min with BIC and 6.9 +/- 2.7 min with placebo (mean +/- S.E.). Blood lactate (BLa) was significantly elevated at cessation of exercise and remained elevated during recovery, but there were no significant differences between treatments. Bicarbonate fell significantly during exercise and recovery in each treatment. At rest, bicarbonate levels were significantly higher in both the P/B and BIC than in the PAK or PLA treatments. Pooled data from the P/B and BIC treatments demonstrated a significant increase in pH at rest and end of exercise when compared to PLA treatment. These data suggest that sodium bicarbonate rather than PAK was responsible for this increase. In summary, our data suggest that in the dosages used in this study, administration of sodium bicarbonate or PAK, alone or in combination, is ineffective in increasing short-term maximal exercise capacity.     

Reliability and validity of a new double poling ergometer for cross-country skiers

Abstract

Thirty-eight competitive cross-country skiers were divided into three groups to assess the reliability and validity of a new double poling ergometer. Group A (n = 22) performed two maximal 60-s tests, Group B (n = 8) repeated peak oxygen uptake tests on the double poling ergometer, and Group C (n = 8) performed a maximal 6-min test on the double poling ergometer and a double poling time-trial on snow. The correlation between the power calculated at the flywheel and the power applied at the base of the poles was r = 0.99 (P < 0.05). The power at the poles was 50 – 70% higher than that at the flywheel. There was a high test – retest reliability in the two 60-s power output tests (coefficient of variation = 3.0%) and no significant difference in peak oxygen uptake in the two 6-min all-out tests (coefficient of variation = 2.4%). There was a strong correlation between the absolute (W) and relative power (W · kg^?1) output in the 6-min double poling ergometer test and the double poling performance on snow (r = 0.86 and 0.89 respectively; both P < 0.05). In conclusion, our results show that the double poling ergometer has both high reliability and validity. However, the power calculated at the flywheel underestimated the total power produced and needs to be corrected for in ergonomic estimations.     

Optimized versus corrected peak power during friction-braked cycle ergometry in males and females

The aim of this study was to compare optimization and correction procedures for the determination of peak power output during friction-loaded cycle ergometry. Ten male and 10 female sports students each performed five 10-s sprints from a stationary start on a Monark 864 basket-loaded ergometer. Resistive loads of 5.0, 6.5, 8.0, 9.5, and 11.0% body weight were administered in a counterbalanced order, with a recovery period of 10 min between sprints. Peak power was greater and occurred earlier, with less work having been done before the attainment of peak power, when the data were corrected to account for the inertial and frictional characteristics of the ergometer. Corrected peak power was independent of resistive load (P > 0.05), whereas uncorrected peak power varied as a quadratic function of load (P < 0.001). For males and females, optimized peak power (971 +/- 122 and 668 +/- 37 W) was lower (P < 0.01) than either the highest (1074 +/- 111 and 754 +/- 56 W respectively) or the mean (1007 +/- 125 and 701 +/- 45 W respectively) of the five values for corrected peak power. Optimized and mean corrected peak power were highly correlated both in males (r = 0.97, P < 0.001) and females (r = 0.96, P < 0.001). The difference between optimized and mean corrected peak power was 37 +/- 30 W in males and 33 +/- 14 W in females, of which approximately 15 W was due to the correction for frictional losses. We conclude that corrected peak power is independent of resistive load in males and females.     

Instrumented bicycle pedals for dynamic measurement of propulsive cycling loads

A system was developed for measuring and analyzing the forces placed on a bicycle pedal during operation of a stationary ergometer. Forces are measured in the plane parallel to the ergometer in directions normal and tangential to the surface of the pedals, encompassing the plane of propulsive forces. The pedals are designed to be structurally and functionally equivalent to standard clipless pedals. The stock pedal spindle and bearing assembly was replaced with a new spindle that was instrumented with two Wheatstone bridges of foil strain gauges. The bearings were relocated to the crank-arm/pedal-spindle interface. The original pedal body was then pinned to the new spindle. Additionally, the pedals were instrumented with optical encoders to measure the pedal angle relative to the crank arm. An optical encoder was also mounted near the bottom bracket to measure crank-arm angle. Signals were transmitted via a cable tethered to the cyclist’s leg from the pedals to an instrumented chassis, where the strain gauge signals were conditioned and the digital optical encoder signals converted to analogue signals. From the instrumented chassis, seven signals are ready for standard analogue data collection. Data collected from this new system has proved to be both comparable with previously published literature and accurate when compared with expected power output values.     

Gross cycling efficiency is not altered with and without toe-clips

The aim of this study was to examine the claim that reductions of 8-18% in submaximal oxygen consumption (VO2) could be due to changing components on a Monark ergometer, from standard pedals without toe-clips or straps (flat pedals) to racing pedals of that era, which included toe-clips and straps (toe-clip pedals). This previously untested assertion was evaluated using 11 males (mean age 22.3 years, s= 1.2; height 1.82 m, s= 0.07; body mass 82.6 kg, s= 8.8) who completed four trials in a randomized, counterbalanced order at 60 rev min(-1) on a Monark cycle ergometer. Two trials were completed on flat pedals and two trials on toe-clip pedals. The Douglas bag method was used to assess VO2 and gross efficiency during successive 5-min workloads of 60, 120, 180, and 240 W. The mean VO2 was 2.1% higher for toe-clip pedals than flat pedals and there was a 99% probability that toe-clip pedals would not result in an 8% lower VO2. These results indicate that toe-clip pedals do not reduce VO2.     

纵跳中关节功率及其与人体疲劳的关系

考察了纵跳中关节功率及其与人体疲劳的关系。 2次纵跳分别在功率自行车上蹬踏 30 s之前和之后进行。纵跳动作用摄像机摄录下来 ,并在运动解析仪上加以分析。纵跳中的地面反力用测力台测量。根据采集的数据计算了关节功率。通过比较 2组数据计算了各关节处关节功率的变化 ,从而得到了对人体疲劳的一种定量描述     

Effect of a novel pedal design on maximal power output and mechanical efficiency in well-trained cyclists

In this study, we evaluated the effects of a novel pedal design, characterized by a downward and forward shift of the cleat fixing platform relative to the pedal axle, on maximal power output and mechanical efficiency in 22 well-trained cyclists. Maximal power output was measured during a series of short (5-s) intermittent sprints on an isokinetic cycle ergometer at cadences from 40 to 120 rev min(-1). Mechanical efficiency was evaluated during a submaximal incremental exercise test on a bicycle ergometer using continuous VO(2) and VCO(2) measurement. Similar tests with conventional pedals and the novel pedals, which were mounted on the individual racing bike of the participant, were randomized. Maximal power was greater with novel pedals than with conventional pedals (between 6.0%, s(x) = 1.5 at 40 rev min(-1) and 1.8%, s(x) = 0.7 at 120 rev min(-1); P = 0.01). Torque production between crank angles of 60 degrees and 150 degrees was higher with novel pedals than with conventional pedals (P = 0.004). The novel pedal design did not affect whole-body VO(2) or VCO(2). Mechanical efficiency was greater with novel pedals than with conventional pedals (27.2%, s(x) = 0.9 and 25.1%, s(x) = 0.9% respectively; P = 0.047; effect size = 0.9). In conclusion, the novel pedals can increase maximal power output and mechanical efficiency in well-trained cyclists.